10th Class Chemistry - Density and Matter

Density

• Mass: The number of particles in a substance
• Volume: The amount of space an object occupies
• V = Length x Width x Height

Physical and Chemical Changes

• Physical change: Alters properties but no new substance is formed
• Chemical change: Alters properties and a new substance forms

Particle Theory of Matter

• All matter is made of tiny particles
• Particles of the same substance are identical
• Particles are always moving; faster with more energy
• Attractive forces between particles are stronger when closer together

Bohr Rutherford Diagrams

• Atoms are most stable when their outer shell is completely full or empty

Classification of Matter

• Alloy: A solution of two or more metals
• Pure substance: Composed of only one type of particle
• Mixture: Composed of at least two different types of particles
  • Mechanical mixtures: Different particles are visible
  • Solutions: Different particles are not visible

Electrical Nature of Matter

• Electrons can change, protons cannot
• Protons are heavy and located in the nucleus. Changing them needs extreme force
• Electrons are light and orbit outside the nucleus. Small forces (like friction) can affect their number
• Opposite charges attract; like charges repel

Charging by Friction

• Rubbing materials together can cause electrons to transfer
• Some materials hold electrons better than others

Charging by Contact

• A charged object touches a neutral object which transfers charge

Charging by Induction

• A charged object is near a neutral object, inducing charge movement in the neutral object

Voltage, Current, and Resistance

• Voltage (V): Energy per charge, measured in Volts
• Current (I): Charge flow per second, measured in Amperes
• Resistance (R): Opposition to current flow, measured in Ohms

Series and Parallel Circuits

• Series circuits: Components are connected one after another; not as bright; turn on/off together; less power; if one breaks, all break
• Parallel circuits: Components are connected across each other; brighter; switches can control individual components; more power; if one breaks, others stay on

Power and Energy

• Power: Rate at which a circuit element "does" something, measured in Watts (W)
• Energy: Total power accumulated, measured in Joules (J)
• Power = Voltage × Current

Energy in Ecosystems

• All energy comes from the Sun

• Sun → Producers → Herbivores → Carnivores/Omnivores

• Carbon cycle:

  • Photosynthesis absorbs carbon dioxide
  • Respiration releases carbon dioxide
  • Fossil fuels release stored carbon into the atmosphere.

• Bioaccumulation/biomagnification: Toxins accumulate in living organisms (especially in top-level predators)

• Solar System: Sun provides energy; Nuclear fusion generates heat and light in stars

  • Tides are produced by the gravitational pull of the moon and sun.

Life Cycle of a Star

• Waxing: Light increase, star growing
• Waning: Light decrease, star shrinking
• Stars start as a stellar nebula, then grow and change based on their mass.
  • Average stars become red giants, then white dwarfs
  • Massive stars become red supergiants, then supernova, neutron stars, or black holes

This quiz covers essential concepts in chemistry for 10th-grade students, including density, physical and chemical changes, and the particle theory of matter. Test your understanding of Bohr Rutherford diagrams and classification of matter with a variety of analytical questions. Challenge yourself to solidify your knowledge in these key areas!